SOUTH AMERICAN NEMATOGNATHI. 15 



bb. Distance of dorsal from tip of snout 2f in the length. Brownish, 

 clouded and spotted with darker. gronovii 4. 



act. A. 7-8. 



d. Length of coracoid processes 1 in the distance between their 

 bases; depth at occiput 2 in the distance between tip of snout 

 and base of pectoral; nuchal plate a thin low crest. bicolor 5. 

 dd. Length of coracoid processes 1-| in the distance between their 

 bases; head without prominent ridges or marginal angles; maxil- 

 lary barbel to second third of pectoral spine. Black, darkest on 

 the sides; head speckled with paler. (Cope.) melas 6. 



ddd. Length of coracoid processes 2 in the distance between their 

 bases; ridges of the head reduced to a minimum; depth at occiput 

 1| in the distance between tip of snout and base of pectoral. 



knerii 7. 



aaa. A. 9; D. 5-6. First dorsal ray nearer tip of snout than to base of 

 caudal; maxillary barbel reaching to middle of pectoral spine. Brown, 

 head dotted with white above; sides and back with dark brown blotches. 

 Dorsal, tips of anal and caudal blackish. (Cope.) aleuropsis 8. 



2. Bunocephalus scabriceps. 



Bunocephalus scabriceps E. & E. Proc. Cal. Acad. Sci., 2d Ser. ii, 

 1889, 49. (Jutahy.) 



This species is distinguished by the extreme develop- 

 ment of the knobs on the head. It is known from the 

 types only. 



Tail slender, tapering. Head and body deep, the 

 depth at base of occipital process scarcely less than the 

 distance from tip of snout to base of pectoral fins. 



Nuchal plate a thin crest with two high knobs, and a 

 knob at its base; a transverse crest at base of nuchal 

 plate directed backward externally; a low crest between 

 the eyes, two crests extending backward becoming ap- 

 proximated behind, forming a lyre-shaped figure; each 

 side of the lyriform crest provided with three knobs; a 

 crest extending from the eye forward and meeting its 

 fellow at the tip of the snout. 



Iriterorbital width equals the snout plus the eye. Eye 

 almost lateral. 



Maxillary barbels reaching about to base of pectoral 



